This application claims foreign priority benefits of Singapore Application No. 200105099-6 filed on Aug. 21, 2001.
This invention relates to microelectronic devices having microelectronic components mounted on substrates and methods of manufacturing such devices. The invention has particular utility in connection with flip-chip packaging.
Microelectronic devices, such as memory devices and microprocessors, typically include one or more microelectronic components attached to a substrate. The microelectronic components commonly include at least one die including functional features such as memory cells, processor circuits, and interconnecting circuitry. The dies of the microelectronic components may be encased in a plastic, ceramic or metal protective covering. Each die commonly includes an array of very small bond pads electrically coupled to the functional features. These terminals can be used to operatively connect the microelectronic component to the substrate.
One type of microelectronic component which is gaining increased acceptance is the xe2x80x9cflip-chipxe2x80x9d semiconductor device. These components are referred to as xe2x80x9cflip-chipsxe2x80x9d because they are typically manufactured in wafer form having bond pads which are initially facing upwardly. After manufacture is completed and the semiconductor die is singulated from the wafer, it is inverted or xe2x80x9cflippedxe2x80x9d such that the surface bearing the bond pads faces downwardly for attachment to a substrate. The bond pads are usually coupled to terminals, such as conductive xe2x80x9cbumps,xe2x80x9d which are used as electrical and mechanical connectors connecting the die to the substrate. A variety of materials may be used to form the bumps on the flip-chip, such as various types of solder and conductive polymers. In applications using solder bumps, the solder bumps are reflowed to form a solder joint between the flip-chip component and the substrate. This leaves a small gap between the flip-chip and the substrate. To enhance the joint integrity between the microelectronic component and the substrate, an underfill material is introduced into the gap between the components. This underfill material helps equalize stress placed on the components and protects the components from contaminants, such as moisture and chemicals.
The underfill material typically is dispensed into the underfill gap by injecting the underfill material along one or two sides of the flip-chip. As shown schematically in FIG. 1, a bead of an underfill material U may be dispensed along one side of the die D. The underfill material will then be drawn into the gap between the die D and the substrate S by capillary action. The direction of this movement is indicated by the arrows in FIG. 1. While such a xe2x80x9csingle strokexe2x80x9d process yields good results, the processing time necessary to permit the underfill material U to flow across the entire width of the die can reduce throughput of the manufacturing process.
FIG. 2 illustrates an alternative approach wherein the underfill material U is applied in an L-shaped bead which extends along two adjacent sides of the die D. By reducing the average distance which the underfill material has to flow to fill the underfill gap, processing times can be reduced. However, this L-stroke approach can lead to more voids in the underfill material, adversely affecting the integrity of the bond between the die D and the substrate S.
Typically, the underfill material U dispensed along the edge(s) of the die D in this process has a relatively high viscosity at dispensing temperatures. This permits a well-defined bead of material to be applied adjacent a single die D, facilitating a more dense arrangement of dies on the surface of the substrate. To get the underfill material U to flow into the underflow gap, the substrate is typically heated sufficiently to reduce the viscosity of the underfill material. This significantly increases manufacturing time and complexity.
Others have proposed pumping an underfill material into the underfill gap through an opening in the substrate. For example, U.S. Pat. No. 6,057,178 (Galuschki et al, the teachings of which are incorporated herein by reference) adds the underfill material via an orifice in the substrate. A viscous underfill material is added to the orifice (e.g., by dispensing it under pressure). The assembly must then be heated to allow the underfill material to flow into the underfill gap.
U.S. Pat. No. 5,697,148 (Lance Jr. et al., the teachings of which are incorporated herein by reference) also suggests dispensing an underfill material into the underfill gap through the substrate. The underfill material is injected under hydraulic pressure through an injection port using a needle. Injecting underfill material using a dispenser such as suggested in this patent and in the Galuschki et al. patent requires precise placement of the dispensing tip in the relatively small opening in the substrate. Fairly complex vision systems must be employed to ensure that the dispensing tip is properly aligned with the opening. Using a small dispenser also makes it more difficult to fill multiple underfill gaps between different die-substrate pairs at one time.
The present invention provides certain improvements in microelectronic devices and various aspects of their manufacture. In accordance with one embodiment, the invention provides a microelectronic device assembly which includes a microelectronic component and a first support. The microelectronic component has a facing surface, an exterior surface, and a first terminal array carried on the facing surface. The first support has a component surface, a mounting surface, a second terminal array, and an aperture which extends through the support from the component surface to the mounting surface. The second terminal array is carried on the component surface and is electrically coupled to the first terminal array of the microelectronic component. The aperture has a first dimension and a second dimension less than the first dimension. The component surface of the support is juxtaposed with the facing surface of the microelectronic component to define a first underfill gap between the component surface and the facing surface. A first underfill material at least substantially fills the first underfill gap.
In an alternative embodiment, the microelectronic device assembly further includes a second support such as a circuit board. In this embodiment, the first support includes a third terminal array on its mounting surface. A second support has a fourth terminal array carried on a terminal surface. The third terminal array of the first support is electrically coupled to the fourth terminal array of the second support. The mounting surface of the first support is juxtaposed with the terminal surface of the second support a define a second underfill gap therebetween. A second underfill material, which may be the same as the first underfill material, substantially fills the second underfill gap.
Another embodiment of the invention provides a method for underfilling a microelectronic component which is electrically coupled to a support to define an underfill gap, with an underfill aperture extending through the support and in fluid communication with the underfill gap. In accordance with this method, a stencil is placed adjacent the underfill aperture, the stencil having a stencil opening in registry with the underfill aperture. The stencil opening defines, at least in part, a fill volume at least as great as the volume of the underfill gap. The stencil opening is filled with a flowable underfill material which is permitted to flow through the support via the underfill aperture and substantially fill the first underfill gap. The stencil may be removed, leaving a completed, underfilled microelectronic device assembly.
Another embodiment of the invention provides a method of manufacturing a microelectronic device assembly including a support and a plurality of microelectronic components. Each of the microelectronic components may have a facing surface carrying a terminal array and the support may have a mounting surface, a component surface carrying a plurality of terminal arrays, and a plurality of underfill apertures. For each microelectronic component, a connecting material is deposited on the terminal array of the microelectronic component and/or an associated one of the terminal arrays of the support. The facing surface of each microelectronic component is juxtaposed with the component surface of the support such that the connecting material electrically couples the terminal array of the microelectronic component with the associated terminal array of the support. The facing surface of each microelectronic component is spaced from the component surface of the support to define a separate underfill gap between each microelectronic component and the support. At least one of the underfill apertures in the support is in fluid communication with each of the underfill gaps. A stencil is placed adjacent to the mounting surface of the support, with the stencil having a separate stencil aperture in registry with each of the underfill apertures in the support. Each stencil aperture defines, at least in part, a fill volume at least as great as the volume of the underfill gap in fluid communication with the underfill aperture with which the stencil aperture is registered. All of the stencil apertures are filled with a flowable underfill material, preferably in a single pass. The underfill material is permitted to flow through the support via the apertures and laterally outwardly therefrom to substantially fill each of the underfill gaps. The stencil may be removed, leaving the final microelectronic device assembly.
In accordance with still another embodiment, the invention provides a method of underfilling a microelectronic component which is electrically coupled to a support such that the microelectronic component and the support define an underfill gap therebetween. According to this method, an underfill aperture in the support is filled with an underfill material. The underfill aperture has a first dimension and second dimension less than the first dimension. The underfill material is allowed to flow outwardly from the underfill aperture to substantially fill the underfill gap. In one particular adaptation of this embodiment, the microelectronic component has a pair of spaced-apart lateral edges and a pair of spaced-apart transverse edges. The underfill aperture is spaced farther from each of the lateral edges than from either of the transverse edges. The underfill material flows outwardly from the underfill aperture a greater distance, and covers a greater surface area, in a lateral direction than in a transverse direction.